Purification of vanadium-containing TiCl{hd 4 {b by heating with TiCl{hd 3{b 0.33 AlCl{hd 3

ABSTRACT

A process for the purification of vanadium-containing titanium tetrachloride which comprises heating vanadium-containing titanium tetrachloride to a temperature of about 120* to 180* C in the presence of TiCl3 . 0.33 AlCl3, and separating the resulting vanadium-free TiCl4 from the solids.

United States Patent 1 1 1111 3,871,874

Winter Mar. 18, 1975 PURIFICATION OF 2,879,131 3/1959 Cauwenberg et al. 423/76 VANADIUM-CONTAINING TICL, BY g g Q ans ey e a. EATING WITH TICL30'33 ALCL3 3,009,772 11/1961 Wigginton 423/76 [75] Inventor; Gerhard Winter, Krefeld, Germany 3,769,233 /1973 Hermans ct al 423/492 [73] Assignee: Bayer Aktiengesellschaft,

Leverkusen, Primary Examiner-Benjamin R. Padgett [22] Filed: Apr. 2, 1973 Assistant Examiner-l3. Hunt I Attorney, Agent, or Firm-Burgess, Dmklage & [2]] Appl. No.: 347,584 S ng Foreign Application Priority Data Apr. 15, 1972 Germany 2218361 57 ABSTRACT Cl /845 423/4921 423/76 A process for the purification of vanadium-containing 423/77, 423/75, 423/612 titanium tetrachloride which comprises heating {51] Int. Cl CZZb 53/00 vanadium containing titanium tetrachloride to a {58] Fleld of Search 75/845; 423/492, 76, 77, peratum of about to 0 C in the presence of 423/75 612 TiCl 0.33 AlCl and separating the resulting vanadium-free TiCl from the solids. [56] References Cited UNITED STATES PATENTS 7 Claims, N0 Drawings 1,770,541 I 1/1956 Singleton 423/76 PURIFICATION OF VANADIUM-CONTAINING TiCl4 BY HEATING WITH TiCl 0.33 AlCl This invention relates to a process for the continuous removal of vanadium impurities from titanium tetrachloride by heating in the presence of TiCl 0.33 AlCl One of the processes currently used for the production of pure white titanium dioxide pigments is the combustion process in which purified titanium tetrachloride is directly reacted with oxygen to form titanium dioxide pigments. The titanium tetrachloride required for this purpose is obtained by the chloridizing dissociation of titanium-containing materials for example, ilmenite, leucoxene or rutile, and contains as impurities a number of other chlorides, predominantly those of iron, aluminum, vanadium and silicon. To obtain a pure white titanium dioxide pigment, it is essential to remove these impurities. One preferred process for purifying titanium tetrachloride is distillation. Titanium tetrachloride boils at 136C and, by distillation, can be separated off from most of its impurities, for example, iron chloride, aluminum chloride and silicon tetrachloride. Vanadium is normally present in the form of VOCl or VCl both of which boil at about the same temperature as titanium tetrachloride. For this reason, the separation of these compounds from the crude titanium tetrachloride by distillation is difficult and extremely expensive.

Several proposals have already been put forward for ways of removing vanadium compounds from titanium tetrachloride. For example, purification methods employing hydrogen sulfide, animal and vegetable oils, fats, waxes, resins, soaps, metals or metal salts have become known. Purifying agents of the kind which can readily be separated off again from the purified TiCl either because they have a different boiling point or because they can be removed in the form of solids, are of particular advantage.

One substance which has a purifying effect upon vanadiumcontaining titanium tetrachloride and which, in addition, has the advantage that it does not introduce any undesirable impurities into the TiCl,, is TiCl or, generally, titanium subhalides. Accordingly, titanium subhalides have been adopted as purifying agents.

US. Pat. No. 2,178,685, relates to a process for purifying vanadium-containing titanium tetrachloride in which a titanium subhalide, for example TiCl is added to the yellow-colored vanadium-containing TiCl After boiling for 2 or more hours, purified TiCl, can be distilled off.

Unfortunately, the long reaction time which is required for the complete removal of vanadium compounds, is a serious disadvantage because considerable quantities of TiCl, are produced and used in the pro duction of titanium dioxide on an industrial scale and, in view of this reaction time, the intermediate purifying stage necessitates extremely large reaction vessels.

It is accordingly an object of the invention to find a quick simple process for the continuous removal of vanadium-containing impurities from titanium tetrachloride.

These and other objects and advantages are realized in accordance with the present invention pursuant to which vanadium-containing titanium tetrachloride is heated to between about 120 and 180C in the presence of TiCl '0.33 AlCl and the purified, vanadiumfree titanium tetrachloride is separated off from the solids.

This process has the considerable advantage that, by virtue of the short reaction time (amounting to a matter of seconds or minutes), purification can now be carried out continuously in vessels of small dimensions, for example a flow tube. No undesirable impurities are introduced or formed by the compound TiCl 0.33 AlCl which represents a solid solution of TiCl and AlCl which is insoluble in TiCl,. Any traces of AlCl which may be given off to the TiCl, are harmless because in any event AlCl is added as a rutilizing aid in conventional methods of producing TiO pigments by the combustion of TiCl.,. In addition, they can readily be removed during the distillation stage, which is normally carried out afterwards in order to separate SiCl, and other chlorides. v

The co-crystallizate TiCl 0.33 AlCl which can be used for purification in accordance with the invention, can be produced in accordance with the processes described in the literature by the reduction of TiCl, with Al-powder. It is a substance widely used in the art, being employed together with aluminum alkylene as a catalyst component for the polymerization of olefins. For this purpose, the compound TiCl 0.33 AlCl is normally subjected to an activating dry-grinding operation, although this does not have any bearing upon the process according to the invention. Ground or unground samples can be used with equal effect for purification.

The reaction on which the purification is based is not altogether clear. However, it can be assumed that the vanadium present in the form of VOCl or, possibly to a lesser extent, in the form of VCl,,, is reduced by the TiCl 0.33 AlCl present into lower-valence, nonvolatile vanadium compounds. The TiCl 0.33 AlCl used in the form of a violet-colored powder is converted into a mass colored from dark brown to black.

The quantity required for the complete removal of vanadium is governed by the vanadium content of the crude TiCl A quantity of about 2 to 15 g of TiCl 0.33 AlCl is normally used per gram of vanadiumcontaining impurity calculated as VOCl a particularly fast reaction, amounting to less than 1 minute at the boiling point, being obtained with a larger quantity. It is preferred to use a quantity of about 3 to 9 g of TiCl -0.33 AlCl per g of VOCI Purification is preferably carried out either at or just below the boiling point of TiCl The yellow color of the vanadium-containing TiCl, disappears almost instantaneously and, after only about 0.5 to 1.5 minutes, it is possible to distil off vanadium-free, completely colorless TiCl (V-content less than 1 ppm). In this case, it is possible to work under normal pressure. However, it is readily possible to carry out purification above the boiling point of TiCl,, in which case it is necessary to work under excess pressure. For example, purification can be carried out at a TiCh-temperature of about to C under a pressure of from about 2 to 3 atms. In this case, the reaction takes place even more quickly than it does under normal conditions. In general, however, the reaction takes place sufficiently quickly at the boiling point under normal pressure.

The purified TiCl is preferably separated off by distillation. To carry out the process according to the invention, the requisite quantity of TiCl 0.33 AlCl can be added to boiling vanadium-containing crude TiCl and vanadium-free TiCl, can be immediately distilled off. This procedure is particularly suitable for the production of highly pure TiCl, on a laboratory scale. The continuous procedure, in which a suspension of TiCl to the second flask. Since the compound TiCl 0.33 AlCl effectively contains 77.6 of TiCl 71.4 g of TiCl in the form of TiCl '0.33 AlCl were thus introduced into the first flask, as against 72 g in the second 0.33 AlCl in TiCl which can be subsequently re- 5 flask, i.e., substantially the same quantities. After the moved from the circuit, is introduced into the incom- TiCl vapor originally present in the apparatus had ing, hot stream of crude, liquid titanium tetrachloride been displaced by the TiCl vapor formed after the adat a given point of the pipeline, followed by transfer to dition, which took from 1 to l.5 minutes, the distillathe distillation stage, is of particular advantage for tion of TiCl was commenced. The distillates were collarge-scale work. By the time the stream enters the dis- 1O lected and examined for their vanadium content at cer tillation apparatus, the purification process is already tain time intervals. The values set out in Table l were over, and the total time in the pipeline is about I to obtained:

Table l g I N Purifying agent time elapsing I|Cl;,0.33 AICL, TiCl after addition distillate from distillate from of the purifying flask l flask 2 agent V-content appearance V-content appearance 1.5 mins 1 ppm crystal- 100 ppm bright clear yellow colorless mins 05 ppm do. 27.6 ppm yellow 90 mins 0.5 ppm do. 9.3 ppm yellowish 210 mins ()5 ppm do 26 ppm pale yellowish minutes, preferably about 1 to 3 minutes, providing the EXAMPLE 2 temperature has been kept at boiling point. In an alternative procedure, a suspension of TiCl 0.33 AlCl in 30 h following arranggmem was .Selected for the TiCl, is initially introduced, incoming hot, gaseous, .Commuous pllrlflcanon T T durcrude TiCl is condensed in the suspension and vanadimg the Chlormanon Tlofcoke mixture. whlcllhad uni-free TiCl is continuously distilled off at another been l by filtlatlon from Suspended solld palucles point of the sump. By the simultaneous, measured inand which comamed 1000 p of vanadium m the troduction of TiCL, AlCl the optimum purification 3s form. of V003 a 3 ppm of Fe m l form of C Conditions can be maintained. was introduced in the form of a continuous stream into However, the purified titanium tetrachloride can also a mlxmg chumbermlo l l pumps?! a uspcnsmn be separated off by filtration because the reaction of i l such a xl l products left after purification are solid, filterable and li %'l2 3 2:22 insoluble in TiCh. In general, however, distillation is 40 fibg fii g 9 3 3 Per f preferred because it is a customary stage in the process e l g g t e mlxmg C amber d for the production of TitCl on an industrial scale. temperature of ho h l t between the The (-14 produced in accordance with the invention mixing chamber and the distillation. still was increased is pure white crystal clear and almost Completely free to boiling point. A distillation still rotating in a heating from Vanadium (v coments less than 05 ppm) It is bath kept at from 170 to 200C was used as the distilla therefore particularly suitable for the production of Tib from Whlch the mflowmg T104 was COmm O l-pigments by the combustion process. In addition, it Q dlsmled f The throughput amounted F 3 l of is particularly stable to light. Even after standing for i and m i durmg Whlch the crude l was several months in sunlight, there are no signs of the yelm Contact with T Alcla was about 5 mmutes low tinges often observed in the case of TiCl which has when thfi a progrgssed to su ch an extent been freed from Vanadium by other methods Accord that the distillation still essentially contained only the ingly, it can also be used as an extremely pure starting l l l residue and the "l was Substance which is particularly suitable for the produc immediately distilled off. lt was possible to increasethe tion of pure titanium compounds and pure titanium throughpul to 5 l P TlCli/h (average Contact time memL 58 about 3 minutes) without VOCL, breaking through by The process according to the invention is illustrated Simultaneously mtervlslfymg the heating of the mixing in the following Examples: chamber, the feedpipe to the distillation still and the heating bath liquid, the temperature reaching almost EXAMPLE l l36C before entry into the distillation still. In both The following tests were carried out to demonstrate 60 a t Was P 0 Obtai a fl fl COIOYIBSS the f t intensive if i ff t f Ti(j|3 33 1 TiCl, distillate with a vanadium content of less than 1 by comparison with TiCl 5 kg of TiCl containing 790 pp ppm of vanadium (VOCl content l3.5 g) were heated to boiling point in each of two spherical flasks EXAMPLE 3 equipped with stirrers and distillation attachments. On e follo ing test arrangement was selected for the reaching the boiling point, 92 g of TiCl 0.33 AlCl- (6.81 g/g of VOCI were added to the first flask and 72 g of standard commercial TiCl (5.33 g/g of VOCl continuous purification of gaseous TiCl containing VOCl Gaseous, crude titanium tetrachloride containing 660 ppm ofV in the form of V061 was condensed into a 2-liter stainless steel vessel which was divided into two halves by a partition reaching almost but not quite to the bottom of the vessel. A suspension of 12 g of TiCl 0.33 AlCl in 108 g of TiCl was introduced into one half at the same time as the gaseous crude titanium tetrachloride, in such a quantity that 5.34 g of TiCl 0.33 AlCl were available per g of freshly arriving VOCl The reaction mixture formed, which was kept at the boiling point of the TiCl gradually passed through under the partition into the second half of the reaction vessel in whose upper part a recirculation evaporator continuously distilled off the purified TiCl and from which the spent purifying agent could be removed into a sump from which additional pure TiCL, was obtained and combined with the main runnings. The pure TiCl was crystal clear and contained less than 1 ppm of V. in this procedure, it was possible to continuously react approximately ll.6 kg of reaction mixture per hour.

The purified products are especially suited for conversion into other titanium products of markedly high purity, e.g. reduction to titanium metal, oxidation to titanium dioxide, and the like.

it will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation and that various modifications and changes may be made without departing from the spirit and scope of the present invention.

What is claimed is:

l. A process for the purification of vanadiumcontaining titanium tetrachloride which comprises heating vanadium-containing titanium tetrachloride to a temperature of about to C in the presence of TiCl 0.33 AlCl and separating the resulting vanadium-free TiCl from the solids.

2. The process of claim 1, wherein the purification is carried out at atmospheric pressure at the boiling point of titanium tetrachloride.

3. The process of claim 1, wherein the TiCl 0.33 AlCl is added to the crude titanium tetrachloride in an amount of about 2 to 15 g per g of vanadium-impurity calculated as VOCl 4. The process of claim 1, wherein the TiCl 0.33 AlCl is added to a stream of hot liquid vanadiumcontaining titanium tetrachloride, the stream is passed through a pipe section heated to about 136C with a residence time therein of about 1 to 10 minutes, and purified TiCl is thereafter separated by distillation.

5. The process as claimed in claim 1, wherein the vanadium-containing crude titanium tetrachloride is introduced in gaseous form into a suspension of TiCl 0.33 AlCl and purified vanadium-free TiCl is distilled off.

6. The process of claim 1 including the further step of reducing the purified titanium tetrachloride to highpurity titanium metal.

7. The process of claim 1 including the further step of oxidizing the purified titanium tetrachloride to high- 

1. A PROCESS FOR THE PURIFICATION OF VANADIUMCONTAINING TITANIUM TETRACHLORIDE WHICH COMPRISES HEATING VANADIUMCONTAINING TITANIUM TETRACHLORIDE TO A TEMPERATURE OF ABOUT 120* TO 180*C. IN THE PRESENCE OF TICL3 0.33 ALCL3, AND SEPARATING THE RESULTING VANADIUM-FREE TICL4 FROM THE SOLIDS.
 2. The process of claim 1, wherein the purification is carried out at atmospheric pressure at the boiling point of titanium tetrachloride.
 3. The process of claim 1, wherein the TiCl3 . 0.33 AlCl3 is added to the crude titanium tetrachloride in an amount of about 2 to 15 g per g of vanadium-impurity calculated as VOCl3.
 4. The process of claim 1, wherein the TiCl3 . 0.33 AlCl3 is added to a stream of hot liquid vanadium-containing titanium tetrachloride, the stream is passed through a pipe section heated to about 136*C with a residence time therein of about 1 to 10 minutes, and purified TiCl4 is thereafter separated by distillation.
 5. The process as claimed in claim 1, wherein the vanadium-containing crude titanium tetrachloride is introduced in gaseous form into a suspension of TiCl3 . 0.33 AlCl3, and purified vanadium-free TiCl4 is distilled off.
 6. The process of claim 1 including the further step of reducing the purified titanium tetrachloride to high-purity titanium metal.
 7. The process of claim 1 including the further step of oxidizing the purified titanium tetrachloride to high-purity titanium dioxide. 